1. Field of the Invention
This invention relates to power monitoring circuits, and more particularly, to a power monitoring circuit for the central processing unit (CPU) on a computer circuit board that can protect the CPU from being damaged or burned out due to the power being supplied to the CPU exceeding the power rating.
2. Description of Related Art
In this information age, computers are becoming an almost indispensable tool for all walks of life. Computers are useful for various applications, such as data processing, multimedia, database, data exchange networking, to name just a few. In a computer system, such as a personal computer (PC), the core element is the central processing unit (CPU). Should the CPU fails or is damaged due to any reasons, the whole computer system may become entirely inoperative. Moreover, the CPU is typically the most expensive integrated circuit (IC) device on a PC mother board. The replacement of a damaged CPU with a good one is therefore quite costly for the user. For these reasons, the CPU on a PC mother board is usually provided with various protective means to protect it from being damaged. One factor that can cause damage to the CPU is an overly large power that exceeds the upper limit of the tolerable power range acceptable by the CPU. To prevent this, the CPU is usually provided with power monitoring means that can constantly monitor the level of the power being supplied to the CPU and make necessary adjustments in the power level or generate an alarm when an abnormal condition in the power occurs.
FIG. 1 is a schematic block diagram showing the architecture of a first conventional power monitoring circuit for monitoring the power being supplied to a CPU 10. As shown, the power monitoring circuit includes an analog-to-digital (A/D) converter 20, a digital comparator 30, an alarm signal generator 40, and a loudspeaker 50.
The A/D converter 20 has an input end coupled to the power input line of the CPU 10 to take the power being supplied to the CPU as an input, and is capable of converting the input signal into a digital signal whose value represents the current level of the power being supplied to the CPU 10. The digital comparator 30 then receives the digital output from the A/D converter 20 and compares it with a preset upper-limit reference value (which represents the tolerable upper limit of the input power to the CPU 10) and a bottom-limit reference value (which represents the tolerable bottom limit of the input power to the CPU 10). These two reference values are preset into the digital comparator 30. If the output of the A/D converter 20 is between the bottom-limit reference value and the upper-limit reference value (indicating that the current input power to the CPU 10 is within the tolerable range), the digital comparator 30 will produce no signal at its output; otherwise, if the output of the A/D converter 20 is below the bottom-limit reference value or above the upper-limit reference value (indicating that the current input power to the CPU 10 is beyond the tolerable range), the digital comparator 30 will output a power-fault signal to the alarm signal generator 40, thus triggering the alarm signal generator 40 to produce an alarm signal which is then converted by the loudspeaker 50 into an audible alarm sound to inform the user or any personnel nearby to take any necessary repair actions.
One drawback to the foregoing power monitoring circuit, however, is that the bottom-limit reference value and upper-limit reference value are fixedly preset into the digital comparator 30. For other CPUs with different power ratings, the settings to the digital comparator 30 should be manually changed, which is quite laborious to do.
FIG. 2 shows a second conventional power monitoring circuit for monitoring the power being supplied to a CPU 10. As shown, this power monitoring circuit includes a power control circuit 60 for controlling the level of the power being supplied to the CPU 10. When the CPU 10 is switched on, it will send out a power-rating code via the signal line 15 to the power control circuit 60. This power-rating code indicates the tolerable range of power that can be accepted by the CPU 10 and can set the power control circuit 60 to adjust for and supply a corresponding level of power to the CPU 10.
The foregoing power monitoring circuit, however, has the drawback that, in the event that the power control circuit 60 fails, the CPU 10 can be damaged or burned out due to the power exceeding the tolerable range and which is unknown to the user.
Most of the computer mother boards are provided with setting means that allows the user to manually set for a suitable power rating for the CPU on the mother board. However, the setting procedure is typically laborious and requires an understanding of the computer hardware. In the event that the user mistakenly set a wrong rating, the CPU could be damaged. Newer models of CPUs are factory-preset with power-rating codes that allow the power monitoring means to automatically adjust for and supply a corresponding power level to the CPU. In user, the power being supplied to the CPU can be continuously monitored by the power monitoring means. In practice, however, the power monitoring means is typically implemented with software. Therefore, in the event that the CPU malfunctions due to inadequate or over power supply, the power monitoring means may fail to function properly due to the software therein being unable to be executed by the CPU. This can cause the CPU to be damaged or burned out.